Step-by-step explanation:
The midline is the average of the lowest point and the highest point.
y = (4 + 6) / 2
y = 5
The amplitude is the distance from the midline to the lowest/highest point:
a = 5 − 4 = 1, or a = 6 − 5 = 1
It's also half the distance between the lowest point and the highest point:
a = (6 − 4) / 2
a = 1
The period is the time it takes to complete a full cycle, so the period is 12 hours.